Research articleThe bioturbation effect of the snail Bellamya aeruginosa on phosphorus immobilisation by drinking water treatment residue in sediment: A long-term continuous flow test
Graphical abstract
Introduction
The necessity of controlling internal phosphorus (P) loading from sediment has been widely accepted by managers and scientists for lake restoration (Zamparas and Zacharias, 2014; Lürling et al., 2016). Many studies have demonstrated that internal P loading is a primary cause of lake eutrophication, especially when external P loading (mainly from human activities) has been effectively reduced (Tammeorg et al., 2016; Paytan et al., 2017). Various physicochemical and biological methods have been tested for the control of such internal P pollution, including in situ aeration and vegetation rehabilitation (Wang and Jiang, 2016). Reduced P mobility in sediment can also be achieved by dosing with inactivating agents (Spears et al., 2014), with effective results reported in various in situ and laboratory studies (Wang and Jiang, 2016). Such agents can include modified clays (Copetti et al., 2016; Wang et al., 2016a, 2016b), modified zeolites (Lin et al., 2019; Zhan et al., 2019), drinking water treatment residue (DWTR) (Wang and Jiang, 2016), and various aluminium (Al), iron (Fe), and calcium (Ca)-based agents (Dittrich et al., 2011; Zamparas and Zacharias, 2014; Lürling et al., 2016).
Understanding the stability of in situ P immobilisation in the context of various environmental factors is essential to developing appropriate strategies for the control of internal P loading in lakes due to the complexity and variation of real-world conditions (Spears et al., 2014; Orihel et al., 2017). Most previous studies have focused on the effect of physicochemical factors (Wang et al., 2016a, 2016b) such as pH (Reitzel et al., 2013), organic matter (de Vicente et al., 2008a; Reitzel et al., 2017), redox conditions (Kleeberg et al., 2013; Meis et al., 2013), and metal ageing (de Vicente et al., 2008b), as P immobilisation is mainly based on physicochemical reactions between P and the metals contained in immobilising agents (Lürling et al., 2016).
The effect of bioturbation has been an inevitable focus during lake sediment remediation (Adámek and Maršálek, 2013). Bioturbation mainly influences biogeochemical cycles through biological metabolism and alterations to sediment physicochemical and biological conditions (He et al., 2015; Baranov et al., 2016; Lukwambe et al., 2018), so its effect on organic and heavy metal pollution control is of particular interest (Janssen and Beckingham, 2013; Men et al., 2016; Cheng et al., 2019). For P cycles, benthic macroinvertebrates can affect sediment P release characteristics through ingestion and alteration of redox conditions (Zhang et al., 2010; Chen et al., 2016; Li et al., 2018). The in situ immobilisation method has typically been based on transforming redox-sensitive P to relatively stable forms (Zamparas and Zacharias, 2014; Lürling et al., 2016), but the effect of bioturbation on sediment P pollution control by in situ immobilisation has rarely been investigated (Wang and Jiang, 2016). Furthermore, existing studies showed inconsistent bioturbation effects, either by reducing control effectiveness (Welch and Cooke, 1999) or having minor undesirable effects on the treatment (Nogaro et al., 2016).
A recent study found that the longevity of the in situ immobilisation method was closely related to three factors: the Osgood index (a morphological index), the ratio of sediment P content to agent dose, and benthic feeding fish (Huser et al., 2016). This suggests that next to the type of in situ P immobilisation method, also the distribution of the immobilisation agent in the sediment is of importance for immobilising P. Heterogeneous distribution of immobilisation agent could lead to differences in immobilisation efficiency, as this has been reported to decrease with the increasing dose of the agents (James, 2011). Therefore, extensive bioturbation was hypothesized to affect in situ immobilisation of internal P in lake sediments by altering the distribution of inactivating agents.
This study investigated the long-term bioturbation effect of benthic macroinvertebrates on in situ P immobilisation in lake sediments using a 350 d continuous flow test. The chosen snail, Bellamya aeruginosa (B. aeruginosa), is a common benthic macroinvertebrate in Chinese freshwater ecosystems (Cai et al., 2012) and has been widely used to investigate the effect of bioturbation on biogeochemical cycles in sediment (Zheng et al., 2011). The chosen immobilisation agent, DWTR, is an inevitable and non-hazardous by-product of drinking water treatment with relatively high concentrations of amorphous Al and Fe due to the use of flocculants for water purification (Ahmad et al., 2016; Jung et al., 2016); its use as an in situ immobilisation agent has great potential for recycling this waste product (Wang and Jiang, 2016). The results were intended to provide research-based support for improved sediment internal P pollution control and to promote the recycling of DWTR.
Section snippets
Sample preparation
Dewatered DWTR was sampled from Waterworks No. 9 in Beijing, China, which uses Al and Fe salts as coagulants. As the collected fresh DWTR after air-drying were block-shaped and variably sized, these were ground and sieved to a diameter of <0.147 mm. Lake water, sediment, and B. aeruginosa were collected from Lake Xuanwu (N 32°04′, E 118°48′) a typical urban Chinese lake just south of the Yangtze River in the city of Nanjing. Surface sediments were sampled from 0 to 10 cm depth and lake water
P concentration
The P concentration in the influent was ~0.00323 mmol L−1 throughout the tests (Fig. 1). In the control box, this decreased slightly (to ~0.00258 mmol L−1) over the first 275 d, then increased substantially to as much as 0.0261 ± 0.0012 mmol L−1. However, the boxes containing DWTR maintained a P concentration ranging from 0 to 0.00113 mmol L−1 in most cases, while those with snails showed no difference in P concentration. These results documented the release of P from sediment without DWTR at
Conclusions
This study investigated the long-term effect of bioturbation by benthic macroinvertebrates (the snail B. aeruginosa) on the stability of sediment internal P pollution control by in situ immobilisation using DWTR. The results showed that the addition of DWTR substantially reduced P concentration in overlying water and tended to reduce N release from sediment, while snail activity had no impact on overlying water properties. Effective P immobilisation by DWTR was mainly related to its Alox and Fe
CRediT authorship contribution statement
Xiaoxiao Shen: Data curation, Writing - original draft, Validation. Nannan Yuan: Visualization, Investigation, Writing - review & editing. Changhui Wang: Conceptualization, Methodology, Software, Writing - review & editing, Validation, Supervision.
Declaration of competing interests
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This work was supported by grants from the National Natural Science Foundation of China (51779244, 41907361, and 51839011), the Natural Science Foundation of Jiangsu Province (Grants No BK20190107), the Fundamental Research Funds for the Central Universities in Jiangsu Province (2019B18314), Natural Science Research Project of Colleges and Universities in Jiangsu Province (18KJD610002), Youth Innovation Promotion Association CAS, and 2019 Support Project for Young Scientific and Technological
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